WO2005105349A1

WO2005105349A1 - Drill to which cbn sintered body is joined

Info

Publication number: WO2005105349A1
Application number: PCT/JP2004/005659
Authority: WO
Inventors: Yasuyuki Kanada
Original assignee: Sumitomo Electric Hardmetal Corp.
Priority date: 2004-04-28
Filing date: 2004-04-28
Publication date: 2005-11-10
Also published as: EP1741506A1

Abstract

[PROBLEMS] To provide a drill having an edge with excellent strength and wear resistance less causing chipping at cutting edges and capable of cutting for a long period even if the drill is used for cutting a hard-to-cut material such as cast iron. [MEANS FOR SOLVING PROBLEMS] In the drill with the pair of cutting edges, cubic boron nitride sintered bodies are brazed to a carbide tool base metal on the drill outer peripheral sides of the pair of cutting edges, the length of the front cutting edge of the cubic boron nitride sintered body (a) joined to one edge of the pair of cutting edges and the length of the front cutting edge of the cubic boron nitride sintered body (b) joined to the other cutting edge are differentiated from each other, and a difference in the lengths of the front cutting edges between the cubic boron nitride sintered bodies (a) and (b) is set to 0.3 mm or longer.

Description

Specification

Dolinore with CBN sintered body

Technical field

The present invention relates to a drill formed by joining a cubic boron nitride sintered body to a cutting edge portion and having excellent cutting edge strength and wear resistance.

Background art

[0002] A CBN sintered body obtained by sintering fine cubic boron nitride (hereinafter, also simply referred to as CBN) using various binders is excellent in cutting high-hardness iron-group metals and iron. The performance is shown. Such a CBN sintered body is used, for example, by being brazed on a carbide tool base material and joined to a cutting edge of a cutting tip or a cutting edge of a rotary tool such as a drill or a reamer (for example, Patent Documents 1 and 2).

[0003] Patent Document 1: JP 2001-150216 A

Patent Document 2: JP 2000-317711 A

Disclosure of the invention

Problems to be solved by the invention

[0004] When the above CBN sintered body is joined to a cutting edge of a drill, a problem may occur in which the cutting edge may be chipped near the rotation axis of the drill. The use of cement is less widespread than for cutting inserts.

[0005] Fig. 2 shows a conventionally known drill for joining a CBN sintered body. In this drill, a pair of cemented carbide cuts is made through a CBN sintered body force S, which has a shape that is substantially rotationally symmetric with respect to the center axis of the drill, and a brazing material mainly composed of soft metals such as Ag and Cu. Joined on the blade. Since the CBN sintered body has higher hardness and higher heat resistance as compared with a cemented carbide, the cutting edge was expected to have a long life and a long combing force.

[0006] In ordinary drilling using a drill, the drill itself rotates and is pressed against the workpiece to cut the workpiece. At this time, the cutting speed at the front cutting edge of the drill has a different value depending on the distance from the drill center axis for each front cutting edge portion. In other words, the closer the front cutting edge is to the drill center axis, the more Since the radius of gyration of the part is smaller and thus the linear velocity of the part is lower, the cutting speed at the part is lower. Conversely, the farther a point on the front cutting edge is from the center axis of the drill, the higher the cutting speed at that point. Therefore, on the outer peripheral side of the drill where the cutting speed is high, by joining the CBN sintered body to the cutting edge of the drill, the above-mentioned excellent properties of the CBN sintered body reduce the wear of the cutting edge. The service life of the drill can be prolonged. However, since the strength of the CBN sintered body is lower than that of the cemented carbide generally used as the drill base material, the boundary portion between the CBN sintered body and the cemented carbide base material on the drill cutting edge and cutting In the area near the center axis of the drill where the speed is low and the cutting force is high, the chip is likely to have chippings and / or chips larger than the chipping of the CBN sintered body. There was a problem that cutting calories was difficult.

[0007] Further, when a CBN sintered body is joined to the entire front surface of a pair of cutting edges of a drill as in the known example shown in Fig. 2, the cutting speed becomes close to 0 immediately near the drill rotation axis, and Since the resistance becomes extremely large, there is a problem that a CBN sintered body having a lower strength than a cemented carbide tends to be chipped and / or chipped. That is, the present invention intends to provide a drill which is hardly chipped at a cutting edge and can perform a long-time cutting process even when used for cutting a difficult-to-cut material such as iron.

Means for solving the problem

[0008] A drill according to the present invention is a drill having a pair of cutting edges, wherein a cubic boron nitride sintered body is brazed and joined to a carbide tool base material on the outer peripheral side of the drill of each of the pair of cutting edges. Yes,

Of the pair of cutting edges, the front cutting edge length of the cubic boron nitride sintered body (a) joined to one of the cutting edges and the cubic boron nitride sintered body (b) joined to the other cutting edge ), And the difference between the front cutting edges of the cubic boron nitride sintered bodies (a) and (b) is not less than 0.3 mm. .

[0009] Further, in the drill, the cubic boron nitride sintered body is arranged from a center axis of the drill.

Distance to (a) !: (mm), distance r (mm) from the center axis of the drill to the cubic boron nitride sintered body (b), and from the outer edge of one cutting edge of the drill Of the other cutting edge The distance to the outer edge D (mm) is related to:

0.12≤ (r X 2 / D) and (r X 2 / D) ≤0.8

1 2

It is preferable that r <r.

1 2

[0010] Further, in the above-mentioned drill of the present invention, the length from the outer end of one cutting edge to the outer end of the other cutting edge of the drill is not less than 5.0 (mm) and not more than 60 (mm). It is preferable.

[0011] Further, in the drill of the present invention, the cubic boron nitride sintered body and the cemented carbide tool base material are joined by brazing via a joining layer. Preferably, it contains 0.5 or 20% by weight of one or two selected from the group consisting of 0.5% by weight, 10% by weight of Cu, and the balance consisting of Ag and inevitable impurities.

[0012] In the above-mentioned drill of the present invention, the cubic boron nitride sintered body and the cemented carbide tool base material are joined by brazing via a joining layer, and the joining layer comprises 20 30% by weight. Of Ti and 20-30% by weight of Zr, with the balance being Cu and unavoidable impurities.

[0013] In the drill of the present invention, the cubic boron nitride sintered body and the cemented carbide base material are joined by brazing via a joining layer. 0.5 to 10% by weight of one or two selected from Zr, 5 to 25% by weight of one or two selected from In and Sn, 15 to 35% by weight of Cu, with the balance being Ag and inevitable It is preferably made of impurities.

[0014] Further, the drill of the present invention is characterized in that the surface of the cutting edge of the drill including the surface of the cubic boron nitride sintered body has a group 4a element, a group 5a element, a group 6a element, Al, Si, and B having at least one element selected from the group consisting of B, or a coating layer made of at least one compound selected from the group consisting of nitrides, carbides, oxides, and solid solutions of the at least one element. preferable.

The invention's effect

[0015] In the drill of the present invention, the occurrence of chipping of the drill cutting edge is prevented and wear is suppressed by brazing and joining a CBN sintered body having a different front cutting edge length to a pair of cutting edges of the drill. And has the effect of extending the life of the drill. Furthermore, the present invention In a drill, a strong bonding strength between them can be obtained by bonding a CBN sintered body to the drill's carbide tool base material through a bonding layer of a specific composition described in this specification. , Can extend the life of the drill. Further, in the drill of the present invention, the life of the drill is extended by coating the surface of the cutting edge of the drill with a coating layer having a specific composition described herein.

It can be even longer.

BEST MODE FOR CARRYING OUT THE INVENTION

[0016] As used herein, the term "front cutting edge length of a CBN sintered body" refers to the CBN sintering on the edge of the cutting edge at the tip of the drill of the CBN sintered body joined to the drill cutting edge. Connect the ends of the body (P and P in Fig. 4) to the center axis of the drill and the outer end of the drill tip (P in

When projecting on a plane that includes 1 2 2, the P and P

1 2

This refers to the difference in distance from the center axis (1 in Fig. 4). Also, if the drill cutting edge is not flat,

1

Fig. 5 shows an example of the length of the front cutting edge in this case. Fig. 5 is a view of the center axis of the drill perpendicular to the paper surface and viewed from the tip of the drill. The cutting edge length of the CBN sintered body a joined to the cutting edge is 1.

The present inventors have studied the life of a CBN sintered body joining drill used for drilling. As a result, on the outer peripheral side of the pair of cutting edges of the drill, the drilling force obtained by brazing and joining the pair of CBN sintered bodies to the cutting edge so that the front cutting edge length of the CBN sintered body is different is obtained. The present invention has been found to have a long tool life in which generation is small and wear progresses slowly, and the present invention has been completed.

A conventionally known CBN sintered body joining drill will be described with reference to FIG. FIG. 2 (A) is a front view of a known drill, and FIG. 2 (B) is a side view of the known drill. In the known drill, CBN sintered bodies a ′ and b ′ having the same shape are arranged on a pair of cutting edges of the drill at rotationally symmetric positions with respect to the central axis of the Dolinole, and brazed. Therefore, in FIG. 2, 1 ′ and 1 ′ are equal and r ′ and r ′ are also equal. For drills in which a CBN sintered body is joined to a cutting edge

2 1 2

The manufacturing method consists of combining the cemented carbide side of the CBN composite sintered body obtained by backing a CBN sintered body with a cemented carbide and integrally / Or, it is a common method to braze through a brazing material made of Cu. FIG. 3 (A) schematically shows the joining state between the cemented carbide tool base material and the CBN sintered body in a conventional drill manufactured using this method. In Fig. 3, M is a cemented carbide tool base material, a 'or b' (represented below by a ') is a CBN sintered body, m is a cemented carbide, and S is a bonding layer made of brazing material. A 'and m together constitute a CBN composite sintered body. As shown in Fig. 3 (A), the boundary between the CBN sintered body a 'brazed to the carbide tool base material M and the carbide tool base material M is formed by the soft brazing joint layer S From In addition, since the brazing material is hardly wet with the CBN sintered body, a gap is formed at the boundary between the cemented carbide tool base material M and the CBN sintered body a '. Therefore, when drilling a work material using this drill, cutting resistance and frictional heat are applied to this boundary portion. Moreover, since the bonding layer S is made of a soft metal, it is rapidly worn due to friction between the work material and the cutting waste.

[0020] That is, with the progress of the cutting process, the cutting resistance is first concentrated near the joining layer S of the cutting edge, or the joining layer S, especially the cemented carbide tool base material M and the CBN sintered body a As a result, clogging of cutting debris occurs in the gap at the boundary of the boundary between the 'CBN sintered body a' and the carbide tool base metal M, and the mechanical load locally increases. In this case, chipping occurs in a relatively low strength CBN sintered body. The present inventors have found a process in which the lack is caused to lead to a larger defect.

[0021] In addition, conventionally, in order to improve the straightness of the drill and reduce the run-out of the cutting edge, it is considered that it is preferable that the sharpness or cutting resistance of each pair of cutting edges is equal, and the conventional CBN sintered body is used. In a joining drill, a pair of CBN sintered bodies that are brazed on a carbide tool base material are designed so that the front cutting edges are equal in length and are arranged rotationally symmetrically with respect to the center axis of the drill. I was The reason for this is that as the cutting process progresses, the wear generated on the flank of the front cutting edge of the drill As described above, the CBN sintered body (for example, a 'and b' in Fig. 2) and the carbide tool base

Since the wear resistance of the material M differs greatly from that of the material M, if the length of the front cutting edge of a pair of CBN sintered bodies (for example, 1 'and 1' in Fig. 2) is different from each other, the amount of wear also differs for each cutting edge.

1 2

This is because it has been considered that the cutting resistance differs between the pair of cutting edges.

[0022] However, the present inventors have questioned the imbalance of the amount of wear between the respective cutting edges. Long before the subject, chipping and even larger chipping occurred at the boundary where the CBN sintered body and the cemented carbide tool base metal were joined. Preventing such chipping, etc. 1S drill life I found it important for extension. That is, the CBN sintered body (a and b) and the cemented carbide tool base are made different by changing the length of the front cutting edge of the CBN sintered body brazed to the outer periphery of the pair of cutting edges of the drill to different lengths. In the vicinity of the boundary with the material M, the CBN sintered body was chipped, and it was found that the drill life could be greatly extended.

Specifically, first, the drill is designed so that the cemented carbide, which is the base material of the cemented carbide tool, acts as a cutting edge near the center axis of the drill, where the cutting resistance is high. Chipping of the CBN sintered body can be suppressed. Then, the length of the front cutting edge of the CBN sintered body brazed to the outer peripheral side of the drill is made different between the pair of cutting edges, so that the CBN is sintered from the center axis of the drill at each cutting edge. The distance to the boundary between the consolidated body and the carbide tool base material can be different. By designing the drill in this way, chipping or wear occurs at one of the pair of cutting edges at the boundary between the CBN sintered body and the cemented carbide base material, and the remaining material that cannot be cut due to the chipping etc. Even if it occurs above, the remaining position does not correspond to the boundary position between the CBN sintered body and the cemented carbide base material at the other cutting edge, so the other cemented carbide cutting edge or CBN sintered body Cutting edge force The residual can be removed. Therefore, even if one of the cutting edges is chipped at the boundary between the CBN sintered body and the carbide tool base material, the same cutting edge must still cut the remaining portion of the cutting material again. In addition, since a large load S is not applied to the boundary of the cutting edge, the occurrence of chipping and wear of the CBN sintered body is greatly reduced near the boundary of the cutting edge and in the location. I found that I could control. Furthermore, by using a brazing material having a specific composition containing Ti, Z or Zr as a brazing material for joining the CBN sintered body and the cemented carbide base material, the wettability of the brazing material with the cemented carbide base material is improved. It has been found that a gap can be hardly generated at the joint between the CBN sintered body and the carbide tool base material.

[0024] A drill according to the present invention will be described with reference to FIG. Fig. 1A is a front view of the drill tip as viewed from the center axis of the drill. Figure 1B shows the same drill as seen from the direction perpendicular to the central axis of Dolinole It is a side view. The drill 1 has a cutting edge 2 and a cutting edge 3, and the CBN sintered bodies a and b are respectively provided on the outer peripheral side of the drill of the cutting edges 2 and 3, that is, on the outer end side of each cutting edge. Brazed to material M. Figure 3 (B) shows the joint of the cutting edge of this drill with the CBN sintered body. CBN composite sintered body consisting of _a and _m , and b and m, obtained by integrally sintering CBN sintered bodies a and b with cemented carbide m The side and the carbide tool base material M are joined by brazing with a brazing material S to form a cutting edge.

[0025] In the drill shown in Fig. 1A, the length from the outer end of one of the drill cutting edges to the outer end of the other drill cutting edge (hereinafter, also simply referred to as the drill diameter) is D, and is the distance from the central axis of the drill. The distance to the outer edge of one of the drill cutting edges (hereinafter simply referred to as drill radius) is 1Z2D. The cutting edge length of the CBN sintered body a joined to cutting edge 2 is 1,

1

The distance to the CBN sintered body is r. On the other hand, the CBN sintered body b

1

The cutting edge length is 1, and the distance from the drill axis to its CBN sintered body is r.

twenty two

[0026] The drill according to the present invention continues even if the material to be cut is left at a position corresponding to the boundary position between the CBN sintered body and the cemented carbide base material on one of the cutting edges and remains. Re, the other cutting edge

When cutting the material, make sure that the boundary between the CBN sintered body and the carbide tool base material does not come to the position where the cutting material is left behind, and also the cutting edge of the CBN sintered body or cemented carbide. The remaining portion can be cut by the cutting edge. In this way, chipping of the CBN sintered body near the boundary between the CBN sintered body of each cutting edge and the carbide tool base material is suppressed. Therefore, the cutting edge length 1 and the force to make the cutting edge length 1 different values If the difference is small, the above-described present invention

2

The difference between 1 and 1 should be at least 0.3 mm, because the effect may not be sufficient.

1 2

More preferably, it is more preferably 0.5 mm or more.

Further, in the drill of the present invention, the distance r from the center axis of the drill to the CBN sintered body a

(mm), the distance r from the center axis of the drill to the CBN sintered body b, and the drill diameter D (mm)

2

Has the following relationship:

0.12≤ (r X 2 / D) and (r X 2 / D) ≤0.8 It is preferable that r <r. In this case, the pair of cutting edges of the drill

1 2

In this case, of the distances to the respective CBN sintered bodies, the shorter one may be determined as r and the longer one as r.

2

[0028] The above conditions are different values for the distance r from the center axis of the drill to the CBN sintered body a or b, and the r and the drill radius (D / 2) r

The ratio of each of 1 2 1 is 0.12 or more, and the ratio of r to the drill radius (D / 2) is 0.1.

twenty two

It shows that it is preferable to be 8 or less. When the ratio of r to the drill radius (D / 2) is less than 0.12, the load on the CBN sintered compact a joined to the drill cutting edge will increase if the cutting force increases sharply near the center axis of the drill. The size of the CBN sintered body becomes large, and chipping and chipping are likely to occur in the CBN sintered body. On the other hand, the cutting speed at each part of the cutting edge increases as the distance from the center axis of the drenole increases. Therefore, the ratio of r to the drill radius (DZ2)

When the ratio exceeds 0.8, the cutting edge at the high cutting speed is made of cemented carbide, and the wear of the cemented carbide cutting edge is significantly increased. Therefore, r and r are preferably in the range of 0.12-0.8 with respect to the drill radius.

2

[0029] In the drill of the present invention, the outer end force of one cutting edge of the drill and the length to the outer end of the other cutting edge, that is, the diameter D of the drill in Fig. 1A D force 5.0 (mm) or more and 6 It is preferably 0 (mm) or less. When the diameter D of the drill is less than 5.0 (mm), the core thickness of the drill becomes small, so that the strength of the drill is reduced and the drill is easily broken. In addition, when the diameter D of the drill exceeds ¾0 (mm), the resistance when cutting the material increases, and a large torque is required to rotate the drill, which exceeds the mechanical power used for general drills. As a result, the desired processing accuracy cannot be secured.

[0030] As described above, in the drill of the present invention, as shown in Fig. 3, a material obtained by backing a CBN sintered body (a and b) with a cemented carbide m and integrally sintering the same is used. The base material M is joined through a joining layer S made of a brazing material. Each of these materials will be specifically described below.

[0031] The cemented carbide tool base material M, the cemented carbide m, and the CBN sintered body a (hereinafter also referred to as "b" in Fig. 1A) shown in Fig. 3 are materials known in the art. Can be used. For example, carbide tool base material M has P, K, and M types specified in JIS B4053. 力 The ability to use any of the cemented carbides. K It is preferable to use K-class for iron materials and P-class materials for steel material processing. Similarly, any of the above P, K, and M cemented carbides can be used for cemented carbide m.K class material should be used in consideration of good bondability with CBN sintered body. Is preferred. The CBN sintered body a is in the range of 35-90% by volume.

Sintered bodies containing CBN are listed in the box. When processing iron materials, 75 to 90% by volume can be used to reduce the steel materials preferred by sintered bodies containing CBN. A sintered body containing CBN in the range of 70% by volume is preferred.

[0032] When a conventionally known brazing material containing Ag or Cu is used for the joining, the brazing material is hard to wet the CBN sintered body, so the cemented carbide m lined with the CBN sintered body and the cemented carbide tool are used. Since only the space between the base material M and the CBN sintered body a is hardly directly bonded to the cemented carbide tool base material M, the CBN sintered body a and the cemented carbide tool base material M A gap is easily formed at the boundary. For this reason, there has been a problem that cutting waste is likely to be clogged in this gap.

In the present invention, the brazing material used in the bonding layer S contains 0.5 to 20% by weight of one or two selected from Ti and Zr, 10 to 40% by weight of Cu, and the balance is Ag. Further, it is preferable to use a brazing material composed of unavoidable impurities. As described above, by adding one or two kinds selected from T and Zr to the alloy of Ag and Cu, the wettability of the brazing material to the surface of the CBN sintered body a can be significantly improved. Thus, brazing joining between the CBN sintered body a and the carbide tool base material M becomes possible. For this reason, the force for eliminating the gap at the boundary portion between the CBN sintered body a and the carbide tool base material M can be reduced or significantly reduced, and it is preferable because clogging of the portion with cutting chips can be suppressed.

When the content of one or two selected from Ti or Zr contained in the brazing material is less than 0.5% by weight, the effect of improving the wettability of the brazing material with respect to the CBN sintered body a does not occur. If the content exceeds 20% by weight, the melting point of the brazing material rises, so that the CBN sintered body “a” tends to be distorted during brazing, and cracking due to the distortion is likely to occur. When brazing the CBN sintered body a to the carbide tool base material M, it is preferable not to braze at a high temperature in order to prevent distortion and cracking of the CBN sintered body a. By setting the Cu content to 10-30% by weight with respect to Ag, the main component, the eutectic melting point drops due to Ag and Cu, and brazing at low temperatures is possible. Is preferable.

[0035] For the same reason as described above, the CBN sintered body a and the cemented carbide tool base material M contain 20-30% by weight of Ti and 20-30% by weight of Zr, and the balance is It is preferable to form a bonding layer S by joining with a brazing material made of Cu and unavoidable impurities, because it is possible to suppress a gap from being generated at a boundary portion between the CBN sintered body a and the cemented carbide base material M. .

[0036] When the brazing material contains Ti and Zr within the above range and the balance consists of Cu and unavoidable impurities, the wettability of the brazing material with respect to the CBN sintered body a is improved by the T and Zr. Since the eutectic melting point drop occurs due to the three elements, the brazing between the CBN sintered body a and the carbide tool base material M can be performed at a relatively low temperature. As a result, it is possible to suppress the distortion of the CBN sintered body a due to heating to a high temperature and the occurrence of deformation due to the distortion.

[0037] For the same reason as described above, the bonding layer S between the CBN sintered body a and the carbide tool base material M contains 0.5 or 10% by weight of one or two selected from Ti and Zr. 5 to 25% by weight of one or two selected from Sn and Sn, and 15 to 35% by weight of Cu, with the balance being Ag and unavoidable impurities. This is preferable because it is possible to suppress the occurrence of a gap at the boundary with the alloy base material M. In this case, when the brazing material contains one or two selected from In and Sn in the range of 5 to 25% by weight, the melting point is lowered and the brazing temperature can be lowered, which is preferable.

[0038] Further, in the drill of the present invention, by using a physical vapor deposition method or a chemical vapor deposition method on the surface of the drill cutting edge, a group 4a element, a group 5a element, a group 6a element, Al, Si , And at least one element selected from the group consisting of B, or at least

It is also preferable to form a coating layer made of at least one compound selected from the group consisting of nitrides, carbides, oxides, and solid solutions of these elements. By forming the coating layer on the surface of the drill cutting edge, the wear resistance of the drill cutting edge surface can be improved, and the life of the drill can be extended.

Example

Hereinafter, the present invention will be further described based on examples, but the present invention is not limited to the examples. Not something.

[Example 1]

The test was performed using a drill having the shape shown in FIG. 1 and having a drill diameter (D) of 25 mm and r shown in FIG. 1 and r having the values shown in Table 1.

2

[Table 1] Table 1

Outer diameter of drill: 25 mm

[0042] The drill 1A IF in Table 1, eight _§: 72 straight weight%, Rei_11: 26 straight weight%, and 1: 2 through the straight weight% force Ranaru brazing material, a pair of cutting edges of the drill After the CBN sintered body was joined to the carbide tool base material in, the diamond cutting wheel was used to grind the cutting edge of the drill. In this example and the comparative example, since the width of the bonding layer S shown in FIG. 3B is extremely narrow, the above r or r at each pair of cutting edges of the drill and the CBN firing of the cutting edge are performed.

1 2

The sum with the front cutting edge length of the body is practically 12.5 mm. In Comparative Examples 1A, 1C, and IE shown in Table 1, the front cutting edge lengths of the pair of CBN sintered bodies of the drills are equal, whereas in the drills of Examples 1B, 1D, and IF, r and r are different and each

1 2

The front cutting edge length of the CBN sintered body at the cutting edge is different. Using the drills shown in Table 1, (1) drilling of iron was performed, and the cutting performance was evaluated based on the number of drillings that could be made before the drill deteriorated. Table 2 shows the obtained results.

[Table 2] Table 2

Work material: F C 200 (iron)

Cutting conditions: Number of rotations of drill 800 0 0 (r p m)

Drill feed amount 0.1 (mm / blade)

Hole depth 30 (mm)

Water-soluble cutting fluid is used.From the results shown in Table 2, the length of the front cutting edge of the CBN sintered body joined to the pair of cutting edges of the drill is different, and a drill with a difference of 0.3 mm or more is used. It can be seen that in Examples 2B, 2D, and 2F, the number of pierced holes significantly increased. That is, it can be seen that the drills of numbers 1B, ID, and IF have excellent continuous machining capabilities. On the other hand, in Comparative Examples 2A and 2C in Table 2, a small chip was found in the CBN sintered body at the boundary between the CBN sintered body at one of the cutting edges of the drill and the carbide tool base material shortly after the test started. This part is left uncut when the work material is cut, and this uncut part strikes the boundary between the CBN sintered body of the other cutting edge of the drill and the carbide tool base material, thereby causing the other part to be cut. Chipping also occurred in the cutting edge CBN sintered body. Due to the mechanism whereby the chipping of one cutting edge promotes the growth of the chipping of the other cutting edge, the chipping of the CBN sintered body at the cutting edge progresses rapidly, and eventually the work material cannot be removed. Due to the occurrence of an extremely large loss of cutting edge, the drill 1A (Comparative Example 2A) and the drill 1C (Comparative Example 2C) were able to drill only a small number of holes. In drill 1E (Comparative Example 2E), r and r forces were lower than those of S drill 1A and drill 1C.

1 2

Due to the high cutting speed at the boundary between the CBN sintered body with the large cutting edge and the cemented carbide base material, the cutting edge made of cemented carbide near the boundary is rapidly worn. on the other hand Due to the rapid wear of one of the cutting edges, the corresponding position on the other cutting edge is also rapidly worn since the cutting edge of the worn part leaves the cutting material. These interacted with each other and the wear of the drill cutting edge progressed rapidly, so the drill 1E was able to drill only a small number of holes.

[0045] On the other hand, a drill 1B having different front cutting edge lengths 1 and 1 of the CBN sintered body (Example

1 2

2B) and Drill 1D (Example 2D) show a case where a small chip is formed in the CBN sintered body near the boundary between the CBN sintered body of one of the cutting edges and the carbide tool base material, and the work material is left uncut. Even in this case, the other cutting edge made of cemented carbide can remove this residue. Therefore, even if a small chip occurs in the CBN sintered body near the boundary between the cutting edge CBN sintered body and the cemented carbide tool base material, the uncut part of the work material due to the chipping is again lost in the CBN sintered body. It is possible to suppress the progress of chipping of the CBN sintered body without applying a large load to the portion where cracks occur. others

For this reason, the tool life was significantly extended in each example with respect to each comparative example. In addition, in drill 1F (Example 2F), the cutting edge of the cemented carbide near the boundary between the CBN sintered body and the cemented carbide base material on one of the cutting edges was worn, and the material was cut. Even if a residue occurs, the other cutting edge of the CBN sintered body cutting edge can remove and remove the uncut portion. This made it possible to suppress the progress of wear of the cemented carbide cutting edge, and greatly extended the tool life.

[Example 2]

As shown in Fig. 1, the CBN sintered body was brazed to the carbide tool base material, the diameter (D) was 34 mm, and the values of r and r shown in Fig. 1 are shown in Table 3. The value of the drill

1 2

A drill performance test was performed using Nore 3A-3E. This test is based on r and r force drilling.

The purpose of this test is to test the effect of 12-mm on cutting performance.

[Table 3] Table 3

Dorinore diameter (D): 34mm

[0048] Using a drill 3A-3G shown in Table 3, a drilling test was performed on iron using the conditions shown in the lower part of Table 4, and the obtained results are shown in Table 4. Table 4 shows the number of holes that could be drilled before normal drilling could not be performed using each drill.

[Table 4] Table 4

Work material: FC250 (錶 iron)

Cutting conditions: Drill rotation speed 5000 (rpm)

Drill feed amount 0.1 2 (mm / blade)

Hole depth 35 (mm)

Use water-soluble cutting fluid. As shown in Table 4, drills 3A to 3G are all drills immediately after starting iron drilling. It can be said that any of the blades without chipping has excellent durability. However, the distance r (mm) from the center axis of the drill to the CBN sintered body joined to one cutting edge of the drill, and the distance from the center axis of the drill to the CBN sintered body joined to the other cutting edge of the drill The distance r (

2 mm) and the diameter D (mm) of the drill:

Drill 3B with 0.12≤ (r X 2 / D) and (r X 2 / D) ≤0.8, and r <r

1 2 1 2

(1) The 3F has a larger number of holes than the drills 3A and 3G, which can be drilled in the workpiece before the end of the life of the drill. This indicates that abrasion is unlikely to occur.

[Example 3]

Next, the effect of the composition of the brazing filler metal used for brazing and joining the CBN sintered body to the cemented carbide base material at the cutting edge of the drill on the durability of the drill was tested. The shape of the drill used in the test was the same as the drill shown in Fig. 1, with a drill diameter of 5 mm and r

0.5 mm, and r is 2 · Omm. CBN sintering using brazing materials 5A-5D shown in Table 5

2

The sintered body was lined with a cemented carbide consisting of 90% by weight of WC and 10% by weight of Co to obtain a CBN composite sintered body. Drills 6A-6D were manufactured by attaching and joining, and polishing the obtained joined body.

[0052] The brazing material was adjusted as follows. That is, a metal powder mixture having the composition shown in Table 5 (the numerical value before the element symbol indicates% by weight) was prepared, and this powder was mixed with an organic solvent to prepare brazing materials 5A-5D. The brazing materials 5A-5D were all pasted. Brazing to the cemented carbide tool substrate of CBN composite sintered body, when the case of using the brazing material 5B-5D with row-,, brazing material 5A in a vacuum atmosphere of 1 X 10- ⁵ torr Was performed in an atmosphere. Table 5 shows the brazing temperature when each brazing material was used. The brazing materials 5A-5D shown in Table 5 all have different melting points due to the different types and compositions of metals contained in the force and other components containing Ag or Cu as the main component. Therefore, the brazing shown in Table 5

The temperature varies depending on the type of brazing material.

[0053] [Table 5] Table 5

[0054] Further, after forming a coating layer of T1A1N with a thickness of 1.Ομπι on the cutting edge surface of the drill 6A and 6D using a PVD method (physical vapor deposition method), each of these drills was used. Table 6 shows the number of holes that could be drilled before carbon steel could be drilled due to the lack of drill cutting edges. The work materials and cutting conditions used for this drilling are listed below Table 6.

[Table 6] Table 6

Work material: S55C (carbon steel)

Cutting conditions: Number of drill rotations 1 5 0 0 0 (r p m)

Drill feed amount 0.1 (mm blade)

Hole depth 20 (mm)

Uses water-soluble cutting fluid

In drills 6A manufactured using a CBN sintered body and a brazing filler metal 5A that is difficult to wet, there is a problem that a gap is formed at the boundary between the CBN sintered body and the base metal of the carbide tool, and this gap is clogged with cutting waste. occured. For this reason, the cutting force is very low at the boundary position of the drill 6A. As the height increased, the CBN sintered body chipped near the boundary, and the chipping widened, so that drill 6A was unable to perform drilling when the number of drillings in the work material was still small.

[0057] On the other hand, drills 6B, 6C, and 6D prepared using brazing materials 5B, 5C, and 5D, which have excellent wettability with the CBN sintered body, respectively, are provided at the boundary between the CBN sintered body and the cemented carbide tool base material. Since there are no gaps in this part, cutting chips are less likely to clog in this part. Therefore, as shown in Table 6, when drills 6B-6D are used, drills 6B-6D are more durable than drills 6A, since drilling can be performed more continuously in the work material than with drill 6A. It was found to be excellent in properties and had a long life.

Brief Description of Drawings

[FIG. 1] A front view (A) and a side view (B) of one embodiment of the drill of the present invention.

[FIG. 2] Front view (A) and side view (B) of a known drill

FIG. 3 is an enlarged view of a portion where a CBN sintered body is joined in a known drill cutting edge (A) and a drill cutting edge (B) of the present invention.

[Fig. 4] Illustration of front cutting edge length of CBN sintered body at drill cutting edge

[Figure 5] Illustration of the front cutting edge length of a CBN sintered body at the cutting edge of a drill

Explanation of symbols

[0059] 1: drill, 2: cutting edge, 3: cutting edge

Claims

The scope of the claims

[1] A drill having a pair of cutting edges, wherein a cubic boron nitride sintered body is brazed and joined to a carbide tool base material on a drill outer peripheral side of each of the pair of cutting edges,

Of the pair of cutting edges, the front cutting edge length of the cubic boron nitride sintered body (a) joined to one of the cutting edges and the cubic boron nitride sintered body (b) joined to the other cutting edge ), Wherein the length of the front cutting edge is different, and the difference between the front cutting edge lengths of the cubic boron nitride sintered bodies (a) and (b) is 0.3 mm or more.

[2] In the drill, a distance r (mm) from a center axis of the drill to the cubic boron nitride sintered body (a), and a distance r from the center axis of the drill to the cubic boron nitride sintered body (b). Distance (mm) and the outer end force of one cutting edge of the drill.

2

Length D (mm) has the following relationship:

0.12≤ (r X 2 / D) and (r X 2 / D) ≤0.8

1 2

The drill according to claim 1, wherein r <r.

1 2

[3] The length from the outer end of one cutting edge to the outer end of the other cutting edge of the drill, wherein the D force is not less than 5.0 (mm) and not more than 60 (mm). Or the drill according to 2 above.

[4] The cubic boron nitride sintered body and the cemented carbide tool base material are joined by brazing via a joining layer, and the joining layer is one or two selected from Ti and Zr. The drill according to any one of claims 13 to 13, comprising 5 to 20% by weight, 1040% by weight of Cu, and the balance consisting of Ag and unavoidable impurities.

[5] The cubic boron nitride sintered body and the cemented carbide tool base material are joined by brazing via a joining layer, and the joining layer is formed of 20-30% by weight of Ti and 20-30% by weight. The drill according to any one of claims 13 to 13, wherein the drill contains Zr and the balance consists of Cu and unavoidable impurities.

[6] The cubic boron nitride sintered body and the cemented carbide tool base material are joined by brazing via a joining layer, and the joining layer is formed of one or two selected from Ti and Zr. .5-10% by weight, In and Sn strengths. 5 or 25% by weight of one or two selected, 15-35% by weight of Cu, and the balance being Ag and unavoidable impurities. Drill described in item 3 or item 3.

On the surface of the cutting edge of the drill including the surface of the cubic boron nitride sintered body, the periodic table 4 &

At least one element selected from the group consisting of elemental elements, group 5a elements, group 6a elements, Al, Si, and B; or nitrides, carbides, oxides of the at least one element, and solid solutions thereof. 17. The drill according to claim 16, comprising a coating layer made of at least one selected compound.